1. Field of the Invention
This invention relates to pneumatic conveying and, in particular, to the conveying of materials which are in the form of thick, heavy pastes which are normally difficult to move and handle.
2. Description of the Related Art
An example of the sort of material with which this invention is concerned is provided by the oil exploration industry. When oil wells are drilled, the cuttings from the drilling operations are brought up onto the drilling platform. For a large part of the drilling operation, a special type of oil is pumped down to the drilling bits as a lubricant. The oil contaminated material which comes up onto the drilling platform has until recently been dumped into the sea. For environmental reasons, such disposal is no longer permitted and the material now has to be transported to the shore for processing.
On the drilling rig, the oil contaminated cuttings are screened to remove a high proportion of the oil for re-use on the rig. The cuttings, which are still contaminated with some oil, are transported ashore in the form of a very thick heavy paste. Typically the material is put into special skips of about 10 ton capacity which are loaded by crane from the rig onto supply boats. This is a difficult and dangerous operation in bad weather and is laborious and expensive.
German Patent Application No. 4010676 describes a device for even, continuous conveying of stiff, solids-containing compositions from a pressure vessel into a pipe- or hose-line wherein, at the outlet of the pressure vessel the material to be conveyed is mixed with the conveying air in a nozzle, while the material to be conveyed is fed evenly to the nozzle by means of a conveying screw. However, such a device suffers from the disadvantage that mechanical agitation is required.